Fuel-air ratio regulator for gas turbine power plants



J. o. sARTo 2,633,704Y

FUEL-AIR RATIO REGULATOR FOR GAS TURBINE POWER PLANTS 4 Sheets-Sheet l Filed Aug. 14, 1947 Num INVENTOR.A T/rzw'a O. Jaffa.

WW1-d April 7, 1953 l J. o. sARTo 2,633,704

FUEL-AIR RATIO REGULATOR FOR GAS TURBIN POWER PLANTS F-iled'Aug. 14, 194': 4 sheets-sheet 2 gaa l0 I ZZ/ 225 20;. 2 Z4, .2/6 201e a 22 e i@ 4, ya .L En.

IN V EN TOR.

April 7, 1953 J. o. sARTo 2,633,704

FUEL-AIR RATIO REGULATOR FOR GAS TURBINE POWER PLANTS Filed Aug. 14, 1947 4 sheets-sheet s April 7, 1953 1. J. o. sARTo 2,633,704

FUEL-AIR RATIO REGULATOR FOR GAS TURBINE POWER PLANTS Filed Aug. 14, 194'? 4 Sheets-Sheet 4 IN VEN TOR.

orma O @a rfa. BY

Patented Apr. 7, 1953 FUEL-AIR RATIO REGULATOR FOR GAS TURBINE POWER PLANTS Jorma O. Sarto, Walled Lake, Mich., assgnor to Chrysler Corporation, Highland Park, Mich., a

corporation of Delaware Application August 14, 1947, Serial N 0. 768,685

(Cl. GII-39.28)

15 claims. 1

This application relates to a control for a burner. More speciiically it relates to controlling a burner adapted to supply products of combustion driving a gas turbine.

An object of the present invention is to provide a stabilizing means for a fuel-burning apparatus. The stabilizing means is advantageously used when the fuel-burning apparatus produces hot gases for a gas turbine, whereby the operation of the turbine is stabilized. It has been determined that the gas turbine should be operated at constant temperature; i. e., the temperature of the gas ydriving the turbine should be constant. At constant-temperature operation the Acurves of turbine output torque against Ispeed and required torque against speed are so nearly parallel throughout much of the operating range that stable operation at constant speed is virtually impossible without involving the speed governor itself. When the turbine drives an airplane propeller, the propeller speed is governed through pitch control, and so in this case an attempt at stable operation will involve an undue amount of propeller-pitch changing. I propose to eliminate this drawback by providing for allowing small variations from the selected constant temperature of gases driving the turbine. In this way the curve of turbine output torque against speed 1s caused to intersect the curve of propeller torque against speed, and stable operation is achieved without a variation beyond the speed range a1- lowed by the propeller governor.

The means providing for departure from the constant-temperature operation of the turbine may take the form adjusted for adjustment of the relation of fuelflow rate to a fuel-pressure diiference that is measured in the fuel path and is normally used to regulate fuel ow in conjunction with an airpressure difference indicative of air-ow rate.

A further object is to associate with the special orice, a means under control of an operator for adjusting the orifice to modify the fuel-air rate to facilitate change to a new speed and to restore the original fuel-air rate when the new desired speed is reached.

Other objects will appear from In the drawings: v

Fig. l is a partially ldiagrammatic view showing a power plant including a gas turbine to Iwhich the disclosure.

lthe controls of the present invention are shown to be applied;

Fig. 2 is a view partially in section showing the application of the controls of the present invention to a fuel-and-air-metering device;

of a special fuel orifice that is Fig. 3 is a fragmentary view of a control used in Fig. 2; and

Figs. 4 and 5 show other forms of controls of the present invention applied to a fuel-and-airmetering device.

Fig. 1 shows a power plant for driving an airplane propeller III. The power plant comprises a compressor I I, a regenerator I2 surrounding the compressor, a plurality of burners I3, and a gas turbine I4. The gas turbine I4 is driven by hot gases produced by the combustion of fuel and air` in the burners I3, and drives the compressor II through appropriate connecting means represented by the reference character I5. The compressor I I, which may be of the axial type, draws in air at its left end through scoops I6. Compressed air is delivered from the right end of the compressor II into conduit means I'I which lead the compressed air to the regenerator I2. The compressed air follows a zig-zag path through the regenerator I2 and is thereby heated by exhaust gases passing from the gas turbine I4 through conduit means I8 to the regenerator I2.

-Heated compressed air passes from the regenerator I2 through conduit means I9 which enclose the burners I3. Each burner is formed of a. fuel nozzle 20 and an air tube ZI formed at an intermediate portion of nested frustum-like sections 22, which permit the air to pass through the tube wall to the nozzles 20. The tubes 2I are curved at their ends to direct the streams of hot gases formed in the burners I3 toward the end of the gas Aturbine It, which is positioned within the burners I3. For a more complete showing of the arrangement of compressor, regenerator, burners, and gas turbine, reference is made to the 'copendi ing application of Staley and Williams, Serial No. 715,840, dated December l2, 1946. For amore complete showing of the burner tubes 2| with the frustum-like sections 22, reference is made to the copending application of Samuel B. Williams, Serial No. 715,873, filed December 12, 1946, now U. S. Patent No. 2,603,064.

The compressor II, which has been previouslyr described as being driven from the gas turbine I4 through means I5, is dri-vingly connected by means 23 with a propeller reduction drive 2A, which in turn drives the shaft 25 on which the propeller I Il is mounted. Thus thepropeller -Iil is driven from the gas turbineV Il at avreduced speed. A propeller speed governor 2t, which includes parts responsive to thespeed of the propeller III is diagrammatically illustrated as regulating a propeller pitch control means 21 through -a connection 28.

Fuel divider 2S is connected with the nozzles 20 through conduits 3| and 32. Fuel is fed from a fuel tank 33 to a booster pump 34 and thence to a transfer pump 35. From the transfer pump 35 the fuel is led by a conduit 35 to a fuel-metering device 31. Thence the fuel proceeds by way of a conduit 38 to a two-pump control 39 and thence through a conduit 45 to the fuel divider 29.

In the conduit means I9 is positioned a plurality of devices 4| responsive to temperature of the air passing from the regenerator I2 to the burners I3. The temperature-responsive devices 4| are connected by means 42 with pressuresensing devices H5 and H 8 in each air scoop I6. The diierence between the pressures sensed by the elements ||5 and H3 is indicative of air-now rate in the scoop and is to be transmitted to the fuel-metering device 31. The temperature-responsive element 4I acts through the connection 42 to reduce the pressure difference transmitted byl an amount dependent upon the temperature in the conduit means I9.

Fig. 2 shows in detail the fuel-metering device 31 and the two-pump control 39. Reference character I4 designates a body which may be formed of several parts and through which fuel is passed for regulating purposes. The body I4 forms part of the metering device 31. rThe line H6 connects the velocity-pressure-sensing element H5 with the body H4, the line H5 having an opening H5a to an air chamber H1, formed in the body H4 below a diaphragm |22. The impactpressure-sensing element H8 is shown to be formed to be part of the body H4 and includes a pressure-compensating nitrogen-filled bellows H8 mounted on the inside of the top of a container H9. Bellows H8a contains nitrogen at some pressure dependent on conditions such as the spring rate of the bellows and compensates for temperature and pressure. The bellows H8a contracts with pressure and expands with temperature and therefore, assumes a position dependent upon density, since density is proportional to the ratio of pressure to temperature. A valve |25 is connected with the nitrogen bellows H8a and is adjustably positioned by the bellows to establish a restriction in a line |25a transmitting the signal received b-y the pressure element H8 to an air chamber |2I formed in the body H4 above an air diaphragm |22, mounted within the body H4. The pressure of air sensed by the element H8 is transmitted to the upper side of this diaphragm, and the pressure sensed by the element H5 is-transmitted to the lower side of the diaphragm through line |53. Whenever air is owing, the pressure on the upper side of the diaphragm |22 will be greater than the pressure on the lower side thereof, and the diiference in these pressures is a measure of the square of the air flow.

The pressure diierence transmitted to the air diaphragm |22y diiers from the diierence between the pressures sensed by elements H3 and H5 because of the action of the temperatureresponsive device 4|. This device 4comprises a body 43, having a valve opening 44, a valve 45 cooperable with the valve opening, a bellows 45 lled, for example, with a liquid, and a bellows seal 41. The body 43 is mounted on a wall 43, which may be part of the conduit means i9. The device 4I also includes a framework 49 mounted on the wall 48 and projecting within the conduit means I9. The bellows 45 is supported on the framework 49, and is connected with an end of a valve rod 55. The valve rod 50 passes through an opening 5| in the wall 48 and passes through and is attached to the bellows seal 41. The valve rod also extends through an opening 52 in an internal shoulder 53 formed on the body 43. A spring 54 acts between the shoulder 53 and the bellows seal 41 to urge the valve 45 and its rod 5D upwardly as viewed in Fig. 2. A line 55 connects the body 43 above the valve opening 44 and the body H4 below the diaphragm H4. A line 53 connects the body 43 below the valve opening 43 and the line I |58.

As the temperature of air flowing to the burners I3 (within the wall 45, Fig. 2, or the conduit means I9, Fig. l) increases, the bellows 46 expands, and the portions thereof connected to the valve rod 55 move downwards, as viewed in Fig. 2, causing the valve 45 to increase the effective size of. valve opening 44 or to decrease the amount of restriction of the opening. Decrease in restriction of this opening reduces the difference in pressures in the lines leading from the sensing elements H5 and H8 to the chambers. |2| and I |1 at the upper and lower sides of the diaphragm |22. Thus for any given condition. in which the valve 45 provides some opening of the valve opening 44, the air-pressure diiierence transmitted to the diaphragm |22 is less than the air-pressure difference at sensing elements H5 and H8, and the greater the effective size of the valve opening 44 due to lowering of valve 45 due in turn to increase in temperature of air iiowing to the burners I3, the smaller the air-pressure difterence transmitted to the air diaphragm |22 for a given. air-pressure difference at the sensing elements H8 and l5. The purpose oi this arrangement will be more fully explained after the balance of the fuel-metering device has been described.

If the bellows 46 and/or the bellows seal 41 fails, the spring 54 will move the valve 45 to the dotted. line position above the valve opening 44, in which position the restriction of the valve opening 45 is very small or non-existent. The diaphragm |22 is held between a collar |24 and a ribbed disk washer |24ETL mounted upon a rod |25. Above the washer is a collar |23, above which is a diaphragm |25, which is secured to bridge portions |21 of the body H4 by screws |28. The collar |23 and a collar |29 clamp the diaphragm |26. The collar has a recess receiving a nut |30 having threaded engagement with the rod |25. The bridge portions |21 are connected by a cover |3| which extends over the top of the rod |25. Clampedbetween-the diaphragm |26 and the bridge portions |21 is a guide |32 having a ange |33 in which the collar |23 slides. The diaphragm |26fis retained in a anged support |34, which is clamped to the bridge portions |21 by the screws |28. The collar |24 rests in a diaphragm I 35, which closes an opening in a wall |35 dividing the body I4 into an air section and a fuel section. Bolts |31 secure the diaphragm |35 to the wall |36. These bolts also support a guide |38 having a flange |39 receiving a collar |40. Collar |40 holds a diaphragm I4I against a ribbed disk washer I4|I1 which rests against a shoulder |42 on the rod |25. The various diaphragms and collars just described are held clamped between the shoulder |42 on the rod |25 and the nut |30 engaging the upper threaded end of the rod |25. The diaphragm |4| divides the fuel section into a metered-fuel chamber |43 and an unmetered-fuel chamber |44. The lower end of the rod |25 is formed as a ball |45, which is mounted in a connecting means |453, which also mounts a ball |45b on the upper end of a rod |46. The lower end of the rod |46 has a threaded portion |41 and a slot |48 for adjusting purposes. The threaded portion |41 engages a movable inner sleeve valve |49, which is slidably mounted in a fixed outer sleeve valve |50. The valves |49 and |50 comprise an adjustable regulating orifice |50a.

The outer valve |50 has an inner annular recess an outer annular recess |52, and connecting radial openings |53. As shown in Fig. 3, the inner valve |49 partially overlaps the inner recess |5| of the outer valve so as to restrict the openings formed therein. The outer annular recess |52 of the'outer valve |50 is in registry with an annular recess |54 formed in the body ||4. The recess |54 is in communication through means not shown, with a supply conduit |55. Fuel comes from ythe fuel tank 33 to the booster pump 34, which may be of the centrifugal type. Thence it proceeds by way of conduits |58 and |59 to the transfer pump 35, which may be of the rotary sliding vane type. The pump delivers fuel through the conduit |55 to the recess |54 in the body |4. Thence the fuel proceeds through the regulating orifice |509- formed of the sleeves |49 and |50 to the unmetered-fuel chamber |44 in the body ||4 below the diaphragm |4|. An orice |6|, formed in a wall |62, connects the meteredand unmetered-fuel chambers.

The fuel orifice |6| is regulated by means of a longitudinally adjustable needle valve |63, to which is connected a pivotally mounted indicator |64, having a point moving along suitable indicia |65, representing desired temperature of combustion products delivered by the burners to the gas turbine. The indicator |64 and needle valve |63 are shown in a mean position. Movement of the needle valve to the left, produced by clockwise angular movement of the indicator, increases the effective opening of the fuel orice |6| and thereby increases the temperature to be reached by the products of combustion of the burners going to the turbine; Movement of the needle valve V|63 to the right produced by counterclockwise angular movement of the indicator l|64 will decrease the effective opening of the fuel orice |6| and thereby decrease the temperature of the products of combustion produced by the burners.

The fuel chambers |43 and |44 above and below the diaphragm |4| are placed in communication by a passage |16 formed in the body 4 and having a restriction |11. The metered-fuel chamber |43'is in communication with a chamber |19 for fuel formed by the cover |3|, the

bridge portions |21, and the 'diaphragm |26.- Communication is established through a passage |80 formed in the body ||4 and having a re` strlction |6| at the end adjacent the `chamber |19. A passage |82 in one bridge portion |21 connects the chamber |19 with a chamber |83, formed below a diaphragm |84 carrying a projection |85 limiting the lower position of the diaphragm |84. Above the diaphragm |84 is a chamber |86, which communicates by a line |81 with the unmetered-fuel chamber |44 through an opening |88. The chamber |83 is connected with a chamber |89 positioned below a wall |90 having an orifice |9| closed by a valve |92, as shown in Fig. 2. Above the wall |90 is a chamber |93, which communicates through a line |94 with the metered-fuel chamber |43. The top of the chamber |93 is formed by a diaphragm |95, which is connected to the stem of the valve |92 and prevents fuel from going from the chamber |93lnto a solenoid |96. The,l solenoid |96 controls the valve |92 through a plunger 91, secured to the stem of the valve |92 in axial alignment therewith. The solenoid |96 is supplied by wires |96a and |96b from a source of electrical power 96. Between the wire |96a and source switch, which comprises spaced terminals |96d and |96e, connected to the line |962, and a contactor arm |96f, controlled by a means |96g responsive to turbine speed. More specifically, the means |96g may be associated with the propellerpitch-control governor. Propeller speed is directly proportional to turbine speed. The propeller is normally constructed so that a certain' pitch produces a given speed range of propeller. Different speed ranges may be preselected, a'nd thus a position of the arm |96f between the contacts |96d and |96e may be produced by different selected speed ranges. The arrangement is such that, when the turbine is operating in the desired speed range, the contactor |96f is positioned between the terminals |96d and |96e and out of con-tact with each of them so that no current flows to the solenoid |96. Under this condition, fuel pressure acting upwardly against the diaphragm |93 causes the plunger |91 to be displaced upwards from a central position in the solenoid |96 and the valve |92 to close the orice |9|, all as shown in Fig. 2. When the turbine is not operating in the desired speed range, the arm |96f will contact one of terminals |96d and |965, causing current to be supplied to the solenoid |96, which now moves the plunger |91 downward to a central position and opens the valve |92, placing the chambers |89 and |93 in communication. A spring |98 acts against the plunger |91 to urge it downwards and thereby provides compensation for a fuel pressure in the fuel chamber |93. The space above the diaphragm |93 is vented by an opening |989. The air chambers ||1 and |2| are connected by a passage |99, which is shown to be closed by a valve 209. A spring 20| is connected at its right end to the body ||4 below the diaphragm |4| in the unmetered-fuel chamber |44. The left end of the spring 20|'is engageable with a flange 292 formed on ythe connecting means |45a so as to provide a yielding limit to upward movement of the stems |25 and |46 and a minimum opening of the regulating orifice |5922 formed by the valves |49 and |59. A rod 292a slidably mounted in the body 4 may be moved upwardly from the position shown to lift the spring 20| and thereby to remove the lower limit on the side of the regulating orice |59a. A threaded member 2021, mounted in the body ||4, provides an adjustable stop engageable with the spring 20| so as to determine the position the spring will assume when the rod 292a is out of the way, as

shown in Fig. 2. A removable cover 202c protects the threaded member 202". The fuel chamber has a drain plug 203.

Fig. 3 shows means for interconnecting the v-alve 200 and the rod 2026. An arm 292d is attached at one end to the valve 209 and has the other end shaped as a pointer 202e, positioned at indicia 2021Y indicating through operating and idling closed and open positions of the valve 200. A link 202g connects a mid-point of the arm 202d and one arm of a bell-crank 202h pivoted at 202i. The other arm of the bell-crank 202h engages one end of the end 202e. The arrangement is such that when the valve 200 closes the passage |99 so that the air diaphragm |22 is |96c .is connected a speed-responsive,

subjectedto the two diiferent air pressures sensed by the elements H and |18, the. be1l-crank 202h has caused the rod 202a to lift the idle spring 20| from the adjustable stop 202% allowing the valve |49 to seek a position dependent on thev air and fuel forces on the diaphragme |22 and |41. At starting and idling conditions it is desirable to have a certain minimum fuel flow that will be independent of gusts of air that might cause the air diaphragm |22. to shift the valve |49. This minimum fuel flow at idling or starting will be higher than -the possible minimum flow during flight conditions when the parts are as shown in Figs. 2 and 3. Accordingly, the arm 202e is moved counterclockwise from the position of Fig. 3 to a vertical position in which the valve 200 opens the passage |99, thereby equalizing the air pressures on the air diaphragm |22. At the same time the horizontal armv of the-bellcrank 202h moves downward, allowing the idle spring 20| to move itself and the rod 202a downward until the spring contacts the stop 202e. Now the valve |49 is free of air-flow forces and is: held in idling position by engagement of the spring 20| with the flange 202.

A fuel line 234 extends from a region of the metered fuel chamber |43 immediately to the left of the fuel orifices and lla. The line 294 splits into branches 205 and. 205, which lead to pumps 202 and 208, which may be ofthe gear type. A relief line 209 is connected to opposite sides of the pump 20'! and contains a relief valve 2|0. Thepump 201 discharges through a line 2|| and a check valve 2|2 from which lead linesV 2|3 and 2|4. The line 214 is formed into two branches 215 and 2 i 6. The latter line leads through a valve 2 I to a dow divider 2 8 from which separate lines go to individual burners. The line 2 I 5 forms part of a bypass for pump 201 and leads to a valve 2 9 formed of a body 220, a sleeve 22| positioned therein, a cover 222 and a balanced piston valve 223 slidable within the sleeve 22|. The line 2|5 leads directly to an annular recess 224 formed in the body 220 about the sleeve 22|. The annular recess 224 communicates with the space between sections 225 and 226 of the piston Valve 223 by way of passages 22? formed, in the sleeve 22|. Passages 223 in sleeve 22| provide communication from the space between the piston valve sections 225 and 22B and a drain line 229 leading back to the line 296. The drain line 229 carries a float valve 230 for eliminating from the line any trapped fuel vapors. The pump 2.08 is provided with a relief line 23| which is connected to opposite sides of the pump and carries a relief valve 232. A conduit 233 leads from the discharge side of the pump 253 and separates into two branches 234 and 235. The branch 234 is connected by a check valve 230 with the branch 2|3 associated with the pump 20?. The branch 235 leads to the valve body 220 and communicates with the chamber between the piston valve sections 225 and 226 by means of openings 231 formed in the sleeve valve 22|. The space above the piston valve 223 is connected by a line 238 with the conduit 204 and subjects the top side of the piston valve to the fuel pressure in the line 204. A coil spring 239 acts against the top of the piston valve 223 to urge it downwardly. An extension 240 formed on the top of the piston valve 223 limits upward movement of the piston valve. A short extension 24| formed on the lower side of the piston valve 223 limits its downward movement. The space below the piston valve 223 is connected by a line 242 having a restriction 243 to the discharge side of the transfer pump |60. Fundamentally, the control valve 2|9 for the. pumps 201 and 208 operates from the difference in intake and discharge pressures at the apparatus included in body ||4. for the upper end of piston valve 2|9 is subjected to the discharge pressure of the apparatus existingl in line 204 and the lower end of the piston valve is subjected to the intake pressure of the. apparatus existing in line |55 as communicated by line 242. Restriction 243 removes the eiect of variations of intake fuel pressure of short duration and also dampens oscillations of piston valve 2|9 from other causes. Spring 239, acting on. the upper end of the piston valve 223 assures that theI piston valve assume a certain position along the length of thev valve sleeve 22| for a given difference in intake and outlet fuel pressures as transmitted` to the ends of the piston valve.

A return line 244r leads from the line 2| 6 to the conduit |59 on the, intake side of the transfer pump 35.y Communication between the lines 2 and 244 is regulated by a piston valve 245 under the control of a speed governor 246 responsive to turbine speed. A relief line 245a containing a relief valve 24T connects the intake and discharge sides of the transfer pump 35. A line 248 leads from the line 244 to the valve 2 i1. During normal operation the valve 2 i1 passes fuel from the line 2 I6 to the fuel divider 2|8. The valve is so constructed that when appropriately regulated, it connects the flow divider with the line 249 for draining the former and lines 2|B and 248 for passing the entire flow of fuel to the discharge side of the transfer pump 35.

ln operation of the above described apparatus, fuel is drawn from the fuel tank 33 through the booster pump 34 through conduits |58 and |59, the transfer pump 35, and the conduit |55 to the body H4, through which it passes to the annular recess |54 and thence through the orifice |53 and annular recesses |5| and |52 in the outer fixed sleeve valve |50 and past the upper edge of the movable inner sleeve valve |49 to the portion of the unmetered-fuel chamber |44 below the diaphragm |4|. From there the fuel moves to the metered-fuel chamber |43 to the left of wall |62 by way of the orifice |64, the size of which is regulated through appropriate adjustment of indicater |64 selectively set in accordancey with .desired temperature` of products of combustion going from the burners` to the gas turbine. The pressure of the fuel is reduced in accordance with the amount of restriction provided at orifice |6| by the needle valve |63, which adjusts the orifice.

Since the unmetered-fuel pressure is greater than themetered-fuel pressure, the diaphragm |4| will be urged upwardly with a force dependent upon th difference between these two fuel pressures, which difference is in turn dependent upon the square of the flow of fuel past the orifice |5| and lle. The upward net force through fuel-pressure difference acting upon the diaphragm 14| is communicated to the rod |25. This upward force on the rod is opposed by a downward force on the rod dependent upon the difference in air pressures acting upon the upper and lower sides of the diaphragm |22 in the air chambers and |2I, which is the air-pressure difference transmitted by sensing elements ||5 and ||8 modied by the temperature-responsive device 4|. When the flow of fuel is proper for the now of air, the air-pressure difference acting downwardly upon the diaphragm 22 is effectively balanced by the fuel-pressure difference acting upwardly on |49 and |50, and the fuel flow decreases.

9 the diaphragm |4I. Thus the valve |49 holds its position, and there is no change in the size of the regulating orifice |50a formed by the valves |49 and |50. Let it be assumed, for the moment, that 4the valve |92 is open. If the flow of air to the burners changes in rate, this change will be sensed by the elements l5 and |8, and a changed difference in pressure will be transmitted to the diaphragm |22. If the rate of air flow increases, there will be a greater air-pressure difference acting downwardly upon the diaphragm |22, and for the moment the upward fuel-pressure difference acting upon the diaphragm |4| will be effectively less than the air pressure differences acting upon the diaphragm |22. As a result, the rods |25 and |46 will move downwards causing the upper end of the movable sleeve valve |49 to provide less of a restriction to the recesses and passages in the outer fixed valve |59. Thus there is an increase in the size of the regulating orifice, and consequently, the fiow of fuel increases. Since the fuel flow increases, the drop in pressure across the orifice |6| increases, and thus there is provided a greater fuel pressure difference acting upwards upon the diaphragm 14|. When the increase in fuel-pressure difference effectively matches the increase in air-pressure difference, downward movement of the valve rods |25 and |46 and of the inner sleeve valve |49 ceases. Thus a new fuel ow has been established, which is appropriate to the new increased air flow. If the air iiow decreases, the opposite of the above described takes place. The effective force of the fuelpressure difference acting upwardly upon the diaphragm |4| is greater than the effective force of the air-pressure difference acting downwardly upon the diaphragm |22, and therefore, the rods .|25 and |49 and the inner sleeve valve |49 move upwardly. This action decreases the size of the regulating orifice |50a formed b-y the valve parts Thus the fuel-pressure drop across the orifice |6| is decreased, and a lower upward pressure acts against the diaphragm |4|. Thus balance is restored between the air-pressure difference acting on the diaphragm |22 and the fuel-pressure difference acting on the diaphragm |4I.

During the above described changes it has been presumed that the valve |92 was open, and this was the case if the turbine was not in the desired speed range, sothat the solenoid was electrically energized to bring the core |91 to its lcwer position. Let it now be assumed that the turbine is operating in the desired speed range. Now the solenoid |96 is no longer energized, and the .plunger |91 brings the valve |92 to closed position under the influence of the fuel pressure acting upwards against the diaphragm |95. Now fuel in the chamber |19 cannot escape by way of the line |82, chambers |83 and |89, orifice |9|, chamber |93 and the line |94, and the only outlet from the chamber |19 is through the passage |90, but this passage has the restriction |8, which provides a time delay to such escape. Thus the volume of fiuid in the chamber |19 cannot change suddenly, and the diaphragm |26 cannot shift its position suddenly. Consequently, the rods |25 and |46 and the inner sleeve valve |49 cannot immediately move upwardly or downwardly in response to `changes in air iiow as transmitted as a pressure difference to the diaphragm |22. The rods and valve |49 can move only if there is sufcient time for fuel to flow through the restricted orifice |81 into or out of the fuel chamber |19. Thus changes in air flow of a. short duration have l0 no eiect upon the fuel flow, for temporarily the inner sleeve valve |49 remains in its original position, and there is no change in the size of the regulating orifice. Keeping the fuel apparatus from being sensitive to air-flow changes of a short duration prevents unstable operation of the apparatus, which may easily occur if the controls are made sensitive to changes of a short duration in the use of the apparatus with the power plant shown in Fig. l.

If the air flow decreases sufficiently, the rod |25 will be urged upwardly with suiiicient force to cause the compression of the trapped fuel in the chamber |19 to act against the diaphragm |84 sufficiently to lift it and thereby to provide the appropriate increase in space for the trapped fuel to permit the upward movement of the rods |25 and |46 and the inner sleeve valve |49 for reduction of the regulating orifice. Lifting of the diaphragm |84 takes place when the pressure in the chamber |19 has through compression risen from metered-fuel pressure up to or just abovethe unmetered-fuel pressure existing above the diaphragm |84. Thus for a large reduction in air ilow there will be immediately provided an appropriate reduction of fuel flow as a precaution against over-heating of the turbine due to too high a temporary rate of fuel-flow rate to air-flow rate. The fuel iiow will not immediately be reduced completely to the point where the ratio of fuel to air iiow is the predetermined value, because this ratio can be obtained only when the pressure in the chamber |19 is the same as that in chamber ||1, and this pressure will be equal only when suicient fuel has escaped from the chamber |19, and this requires time. The error represented by the difference between the fuel flow actually existing under this condition and the theoretically correct fuel iiow for the actual air flow will be always approximately the same percentage of the fuel flow, since the diaphragm |84 is subjected to the difference between meteredand unmetered-fuel pressure, which is a measure of fuel flow. A large increase in air ow will not immediately have the same effect, because the resultant increase in downward thrust upon the air diaphragm |22 will only tend to increase the volume of fuel trapped against immediate release from the space |19 and associated parts. This will tend to move the diaphragm |84 downwards to achieve compensation by reduction of the size of the chamber |83, but the projection |85, attached to the diaphragm prevents downward movement of the diaphragm.

Under starting conditions, it may be desirable to use a minimum rate of fuel flow higher than is possible when the idle spring 20| is raised to the position of Figs. 2 and 3 by the rod 2029. In this event, the arm 202d is shifted counterclock- Wise to make the valve 260 open the passage |99. The arm 202d acts through the link 2112g to lower the horizontal arm of the bell-crank 20211. Now the aforesaid horizontal arm provides no opposition to movement of the rod 202e, and the spring 20| moves against the stop 2029. Now air-flow rate exerts no fuel control, since the passage |99 equalizes the pressures at opposite sides of the diaphragm |22. The fuel-flow rate is higher than the possible minimum obtainable in the relative position of parts of Figs. 2 and 3.

It has previously been assumed that the temperature of air flowing to the burners has not changed, and therefore, that the temperatureresponsive element 4|` has not acted through various described control means to adjust its valve 45 with respect to the valve opening 44. If now the temperature of air going to the burners increases, the valve 45 is moved downwards by the bellows 46, reducing the restriction of the valve opening 44. This means a greater difference between the air-pressure difference sensed by elements I I and IIB and the pressure difference transmitted to the diaphragm I2I. Thus as the temperature of air flowing to the burners increases, the apparent air-flow rate in the form of pressure difference on diaphragm |22 decreases, although the actual air-flow rate may remain constant, as sensed by the elements I|5 and II8. Since the air-pressure difference acting on the diaphragm |22 is decreased, and the fuel-pressure difference acting on diaphragm I4'I is presumed Vto remain constant for the moment, the unbalance will move the inner valve |49 up, reducing the Vsize of the regulating orice |50EL to produce a lower fuel-flow rate that will just balance the apparently reduced air-flow rate. Decrease in the temperature of air flowing to the burners has the opposite effect. In this case, the bellows 46 contracts, moving the valve'45 toward the valve opening 44 to increase the restriction of the latter. This will reduce the difference between air-pressure difference sensed by elements |`I5 and IIB and air-pressure difference 'acting on diaphragm |22. If the 4actual air-'flow rate remains constant as maybe assumed, the apparent air-flow rate or the air-pressure difference acting on diaphragm |22 increases, causing the valve |49 to be moved downwards and the size of the regulating orifice |50a to be increased. This produces an increased fuel flow, increasing the pressure drop across the orice I6I to restore ybalance `between the fuel-pressure forces acting against the diaphragm I4I and air-pressureforces acting on diaphragm |22. Thus the air-now rate has lremained the same, while 'the fuel flow rate has increased, and so lthere has been vprovided an increase in the ratio of fuel flow Yto air flow. Thus there is provided a compensation for the decrease in the temperature -of air iiowing to the burner in maintenance of aconstant temperature of products rof combustion flowing from the lburners to the turbine.

If a greater temperature is desired for the `products of combustion passing from the burners to the turbine, indicator |64 is moved to aclockwise Vdirection `thereby moving the needle `valve |63 to the left -and increasing the effective size of the orifice I6I. Thus, for the moment, the pressure drop across the orifice is reduced, `for the fio-w of fuel remains constant, and the `fuelpressure difference acting upwardly against the diaphragm I4I is reduced. Thus the balance be- .tween the air-pressure -fcrces Aand the fuel Apressure forces is disturbed, and thus sleevevalve l|49 .moves downwardly increasing the regulating 4oriceformed between the valves |49 andI'50. This increases lthe fuel flow Yand the pressure 'drop across the `orifice IBI. 'I'hus balance is restored between the .diaphragms |22 and I4I. The airflow rate has remained the same, and the fuel flow rate has increased. Thus there is an increase in the ratio of fuel .flow Vto `air flow, and since the temperature yof :air flowing vto the burners has been assumed Ato remain constant, the increase in ratio of fuel to air must Lresult in a greater temperature of products .of .combustion produced by the burner. Similarly the temperature of products of combustion maybe reduced by greater restriction of the orifice I6I by the needle valve |63.

After the fuel passes through the metering orice I6I, it goes through the vconduit 204 to the pumps 201 and 208. If the pump 201 is functioning properly, the ventire output of the pump 208 will be bypassed, with the parts in the position shown in Fig. 2, through the openings 231, the space between the piston valve sections 225 and 226, the sleeve openings 228, and the return line 229 back to the intake side of the pump 208. A portion of the output of the pump 201 will be bypassed through the line 2I5, the sleeve openings 221, the space between the piston valve sections 225 and 226, the valve sleeve openings v228, and the return line 223 to the intake side of either pump 268 yor pump 201. The portion of `thepump 201 that is `not bypassed as aforesaid, is delivered through the line 2 I6 and the valve 2 I1 to the ow divider 2 I8, whence it proceeds to the individual burners. The position of the valve 223 will determine the relative portions ofthe output of the pump 201 that 'are bypassed through the line 2I5 and delivered to the burners through the line 2 I 6. The position of the valve A223 is determinedby the pressure of fuel above the valve piston Asection 225, which is determined by the diierence between the pressure `existing in the line 204 leading to the pumps 201 and 2 I8 and the pressure in line 242, with the aid of a coil acting against the valve piston section 42725. The force exerted by spring 239 is substantially constant in allpositions and is adapted to balance a difference in pressure normally always existing Vbetween line y42 and line 204. If it be assumed that the pressure in line 242 is constant (and this is generally the case), then the greater the pressure in the line 204, the lower the 4position of the vvalve 223, the more the piston valve section 225 covers the ports 221, the less the amount of output lby the pump 201 bypassed through the line 2 I5 and the sleeve valve openings 221, and the greater the amount of the output of the pump 201 'going through the line 2I6 to the iiow divider 2I6 and to the openings. Thus 'there is a 'tendency to maintain the constant pressure in the line 204 or on the intake side of the pumps 201 and 208, for the greater this pressure becomes, the greater the relative amount of the Apump output delivered to the burners. VIf Dump -201 fails, presumably the `output Ypressure of the pump falls very low, and the .fuel pressure on `the intake side reaches a high level. Consequently, two things happen: pump 208 delivers fuel through line 234, check valve 236, and 'lines 2I3, 2I4, and `2'I6 to 'the iiow divider 2 I 8; and the piston valve :223 is depressed under the increased fuel pressure in the line 204 Yuntil the sleeve valve openings 221 are completely closed, and the sleeve valve 'openings 231 are at least partially closed, thereby reducing the amount of fuel bypassed from pump 208 by way of line 235 and return line 229. If pump 201 again functions properly, pressure inthe line 204 will be sufciently lowered as a result of fuel delivered by pumps 201 and 208 to cause the piston valve 223 to rise until the output of pump 208 is bypassed by virtue of complete uncovering ofthe valve openings 231, and a portion ofthe output of pump 201 may be bypassed bya partial uncovering of the valve openings 221.

The apparatus of Fig. 4 is similarto that of Fig. 2, except that there is a device 245 that operates temporarily to increase or decrease the fuel-flow signal in accordance with a temporary increase or decrease in the vair--fio'w signal, to make the fuel-flow rate constant in spite'of changes in'airflow rate `of Vshort duration. The apparatus of Fig.. 4 includes the velocity pressure element ||5 and the impact pressure element |l8 transmitting air pressures to the lower and upper sides of the air diaphragm |22. The temperature-responsive device 4| acts through the lines 55 and 56 to modify the air-pressure difference from the sensing elements I| and I|8 transmitted to the air diaphragm |22 so that compensation is obtained for variation in temperature of air flowing through the conduit means I9 to the burners I3. The fuel diaphragm |4| is subjected on the one side to metered-fuel pressure existing in the chamber |43 and unmetered-fuel pressure existing in the chamber |44, there being a difference between these pressures because of the orifice I 6| controlled by the needle valve |63 through an indicator |64 positioned in accordance with desired temperature of combustion products issuing from the burners I3. The air and fuel diaphragms |22 and |4| act through rods |25 and |46 to adjust the inner valve part |49 forming with the outer valve part |50 the regulating oriflce |506. Thus the regulating orifice |50'L is adjusted to maintain a predetermined ratio of fuelow rate to air-fiow rate, which ratio may be varied by the temperature-responsive device 4| to maintain a predetermined temperature of combustion products issuing from the burners to the turbine.

The device 245 has a body 246 in which is formed a plurality of passages to be described presently. Mounted in the body 246 is a diaphragm 241, which with the body 246 forms a .chamber 248. A variable-rate or non-linear spring 249 acts against the diaphragm 241 to move. it downwardly. as viewed in Fig. 4. A diaphragm 250 is mounted in the body 246 and has a restricted opening 25| The diaphragms 241 and 250 together with the body 246 form a chamber 252. A diaphragm 253 is mounted in the body 246. The diaphragms 250 and 253 form with the body 246 a chamber 254. A rod 255 is connected to the diaphragms 241, 250, and 253 and to a diaphragm 256 forming part of one wall of a container 251 having restricted openings 258 and ,259. The container 251 includes a stem part 260 which has a valve portion 26| and a restricted passage 262. The valve portion 26| is engageable with a seat 263 formed in the body 240. The stem 260 is attached to a small diaphragm 264 and a large diaphragm 265 mounted in the body 246 and forming therewith chambers 266 and 261. When the valve 26| closes the opening 263, there is formed a chamber 268 with the aid of the housing 246 and the diaphragm 264. Communication is established between the chamber 268 and the discharge line 204 by a passage 269 in the body 246 and a line 210. Between the diaphragm 253 and an interior wall 21| in which the opening 263 is formed, there is formed a chamber 212. Communication is established between the chamber 212 and the unmetered-fuel chamber |44 through a passage 213 in the body 246 and a line 214. lSince the metered-fuel chamber |43 is in direct communication with the discharge line 204, which communicates with the chamber 268 in the body 246 through the passage 269 and the line 210, the chamber 268 is at metered-fuel pressure. Since the chamber 212 communicates with the unmetered-fuel chamber |44, the chamber 212 is at unmetered-fuel pressure. The drop in pressure across the valve opening 263 in the body 246 is equal to the difference between unmeteredand metered-fuel pressures in the chambers |44 14 and |43, which 1s a drop in pressure across the metering orifice |6|.

The wall 21| in the body 246 carries a flange 215, which engages one end of a coil spring 216. The other end of the spring is engaged by a flange 211 formed on the container 251. A passage 218 and a restricted passage 219 connect thev chamber 266 with passage 269, and the passage 218 and a restricted passage 280 connect the chamber 261 with the passage 269. A passage 28| in the body 246 connects the passage 213 with the chamber 248 and thereby places this chamber at unmetered-fuel pressure. The chamber 248 is connected to the passage 269 by a passage 282 having a restriction 283.

A lever 284 in the chamber 254 is pivoted on the rod 255 at an intermediate point, as indicated at 285. One end of the lever 284 is pivotally connected as at 286 to a rod 281 attached to diaphragms 288 and 289. The rod 281 carries a piston 290 which fits spaced aligned bores 29| and 292. A portion 293 between these bores is of larger diameter. A passage 294 connects the chamber 212 and the portion 293. A passage 295 connects the bore 29| and the chamber 266. A passage 296 connects the bore 292 and the chamber 261. A passage 291 connects the chamber 254 and a chamber 298 beyond the diaphragm 289. At the end of the lever 284 opposite the end to which the rod 281 is connected, there is pvotally connected, as indicated at298, one end of a link 299. The other end of the link 299 is connected to an arcuate slot 300 formed in a member 30| pivoted on a shaft 362. The shaft 302 projects from the body 245, and a control stick 303 is secured to an external portion of the shaft 302 in a manner not shown. The position of the one end of the link 299 in the slot 300 in the member 36| is controlled by aneroid bellows 304, which is connected at one end by a part 365 with the link 299 and at the other end to a part 306 with the member 30|. The sens-- ing element ||8 is connected with the chamber 254 in the body 246 by a passage 301 in the body 246 and a line 308, and thus the chamber 254 is subjected to the air pressure sensed by the element ||8. The chamber 252 is connected with the sensing element ||5 by a passage 309 in the body 246 anda line 9|0, and thus the chamber 252 is subjected to the air pressure sensed by the element ll5.

As previously mentioned, the air and fuel diaphragms |22 and I4| control the inner movable valve part |49 of the regulating orifice |50a to adjust the fuel-fiow rate in accordance with airflow rate in order to maintain a predetermined ratio of air-fiow rate to fuel-flow rate. This ratio is modified by the temperature-responsive device 4| in inverse relation to the temperature of air going to the burners in order to maintain a predetermined temperature of combustion products issuing from the burners. If it is desired that the temperature of the combustion products be changed, then the needle valve |63 is adjusted.

Let us now consider the effect on the fuelfiow rate of changes in air-now rate of short duration. Assume, for example, that the air-fiow rate increases. This means a greater difference between pressure sensed by the elements ||5 and ||8 and a greater downward force on the air diaphragm |22 tending to increase the size of the regulating orifice |50@ The aforementioned increase in pressure difference sensed by the elements |i5 and |18 acts against the diaphragm 256 in the body 2116, so as to move tthe diaphragm, the rod 255, and :the .diaphragm :256 upwards. The container 251 will also `be moved upwards, since the volume of the container is temporarily fixed, Vbecause the .container `has only restricted openings S, 255and 282. The valve 26| attached to the containei` .257 is movedupwards, increasing the pressure drop across the opening 263. Since the chambers .212 .and 26B at opposite sides of the valve opening l263 .are directly connected with `the chambers `lili .and 1&3 .at opposite sides :of the fuel .diaphragm |4I., the `difference in vpressure between .the chambers |24 and `|23 .is increased, and thereby a .greater upward force is exerted on the fuel diaphragm IM. This greater upward force on the fuel diaphragm balances the aforementioned greater downward force on the air diaphragm due to increased air now. Thus there is no immediate adjustment of the regulating orifice |522, and consequently, no increase in fuel-flow rate. If the change in air-now rate is only of short duration, the force acting on the .air diaphragm |22 will return to its original value, and the force on the diaphragm 255i in the body '245 will also return to its original value bringing the valve 26| to its original'position accompanied by the orig# inal pressure drop across the opening 263, and the fuel-flow rate will continue without change.

However, if the change in air-flow rate has more f;

than a short duration, the restricted openings 258, 259, and 262 inthe container' 251 have time to :allow sufficient iiuid to enter the container 251 .to enable the container to return to its originalposition under the influence oi the coil spring 2.15 bringing about the original position of the valve 26| and the restriction of the opening 263, in spite of the fact that the diaphragm 256 forming part of the container 251 has moved upwards because ofthe increased upward force acting on the diaphragm 255 due to increase in airilow rate. Since with the passage of time therestriction of the opening 263 has returned to its original value, the pressure drop across the opening 263 or the diierence between thepressures in the unmeteredand metered-fuel chambers |44 and |43 is decreased toits original value. This means that the increased downward force on .the air diaphragm |22 due to increased airflow rate may now move Vthe inner valve part |49 downwards to increase the size of .the regulating orifice |5611. Thus the fuel-flow rate is increased in accordance with air-flow rate in maintenance of a predetermined ratio of fuel flow rate to air-How rate.

If the air-flow rate decreases for a short time, the opposite of the aforedescribed takes place. Decrease in air-ilow rate means decrease in air pressures sensed by the elements H5 and IIB and a decrease in the downward force acting on the air diaphragm |22. This should otherwise cause the inner valve part |49 to rise to decrease the .size of the regulating orince |50e, but in the meantime, the upward force on the diaphragm 256 has decreased because of decrease in air-now rate. Because of the spring `229 acting against the diaphragm241 and in turn against the rod 255, the decrease in upward force on the diaphragm 250 results in a downward movement of the rod 255 and the diaphragm 256. Because the openings 258, 259, and 262 in the container 251 are restricted, downward movement of the diaphragm 256 first brings about downward movement of the container 251 and its associated valve portion 26| against the action of the coll 16 spring y27H5. Downward .movement of the yvalve 26| .decreases the restriction .of the .opening 263. thereby lowering the pressure drop across the opening 263 between the vchambers 212 and .268 and the chambers |44 and |43. This means that the fuel in the chambers |44 and |43 exert a smaller upward `force on Vthe fuel diaphragm |4| -which force just balances the smaller downward force acting on the .air .diaphragm |22 due to decreased yair-flow rate. If the air-flow rate increases to its previous value after just ra short time .the downward force on the air diaphragm |22 lwill increase to its original value, and .at the same time the `upward force .on the diaphragm 25D will likewise increase causing the Vvalve 26| Vto be returned `to its .original position. This increases ythepressure drop .across the opening 263 or 'the difference fin .pressure rbetween the fuel chambers |44 and |43, and thus there is an increase to original value of the upward force acting on the fuel diaphragm |4|, which balances the increase to original vvalue of the downward force on air diaphragm |22. Thus the inner valve `part lM19 :does not move, andthe size of the regulating orice e vis maintained. If the aforementioned .decrease in air-ow rate continues, lthe restricted openings 258, 259, and 262 in the container .2.61 have time to allow the expulsion of iiuid from the container 251, and the container and .the valve 26| move upwards to their original position under the action of the spring 226, in spite .of the fact that the diaphragm 25|] and the rod '.255 have caused the diaphragm 256 to assume the lower position. Withthe valve 26| returned `to its original .position, .the restriction of the opening 263 has been increased causing a greater diiference in fuel pressures in .the chambers |43 and `|41! and a greater upward force, .or a :return to the original value -of upward force, acting on the fuel diaphragm IM. Since the decrease in air-flow rate has produced a decrease in downward force acting on the air diaphragm |22, the inner valve part |49 moves upwards to decrease the size of the regulating orice |564, andthe fuel-flow rate is decreased :in accordance with the .air-flow rate.

Let Ius fnow consider the operation of the control -stlck `363 :and its associated parts. If the right end of .the :stickis moved upwards from the position `shown in Fig. 4, this motion will be transmitted through the .shaft 302, the member 35|, and the link ,229 zto the right end of the lever 284, causing it tomove upwards about the connection 285 of the 'lever with the rod 255 .as a pivot. Accordingly, the left end of the lever 284 moves downwards, bringing the Ypiston 296 into the bore `29| or .into restricting relation with respect to the -end of the bore 29|. Thus connectionbetween the chamber 212 Vand thechamber r261 is broken or restricted 4by way of the passages 294 and 29.5, 4and the chamber 261 is placed at the metered-fuel pressure existing in ie chamber'266, by virtue of the connection between they chambers through .the passages y269. 218 and 280. Since the chamber '261 was previously at unmmetered-fuel pressure, the pressure in the chamber has been decreased, and accordingly, the unmetered-fuel pressure in the chamber 266 causes the diaphragm '265 to move downwards, lcarrying with it the stem portion 26|! of the'container 251 and the valve 26|. The valve 26| by moving vdownwards decreases the restriction of the opening 263 and also the pressure 4drop across the opening 253 or the pressure difference between chambers 212 and v258 or 17 chambers I 44 and |43 and an upward force acting on the fuel diaphragm |4 I. Since the downward force acting on the air diaphragm |22 remains constant because of a presumed constant air-flow rate, the downward force on the air diaphragm is now larger than the upward force on the fuel diaphragm I4I, and the inner valve part |49 is moved downwards to increase the size of the regulating orifice |5614. Thus the fuel-ow rate is increased, and likewise the ratio of fuel-flow rate to air-flow rate. If the right end of the control stick 303 is moved downwards, there will result an upward movement of the piston valve 296 into a position in the bore 29|, in which connection of the chamber 266 with the unmetered-fuel chamber 212 by way of the passages l294 and'296 is cut off. Now the pressure in the 219. This decrease in the pressure in the chamber266 means a decrease in the net downward force acting on the stem 266 through the small and large diaphragms 264 and 265, and the valve 26| is moved upwards, increasing the restriction of the opening 263. This brings about an increase in pressure drop across the opening 263 and in pressure diierence between chambers 212 and 268 or chambers |44' and |43 and an increase in upward force acting on the fuel diaphragm |4|. Since the downward force on the air diaphragm |22 remains constant because of a presumed constant air-flow rate, the increase in upward force on the fuel diaphragm will move the inner valve part |49 upward, reducing the size of the regulating orifice |5611. The result is a decrease in fuel-flow rate and a lower ratio of fuel-flow rate to air-flow rate. When, as

aforesaid, the piston valve 296 moves down into the bore 29|, the pivot point 285 of the lever 284 on the rod 255 will also move downwards somewhat for a short time, because the resultant decrease in fuel pressure in the chamber 261 causes the container 251 with its restricted openings 268, 259, and 262 to move the diaphragm 256 and the rod 255 downwards. This downward movement of the pivot point 285 of the lever 284 is only temporary, because with time sulcient iiuid may enter the container 258 by way of the restricted passages 258, 259, and 262 to permit the diaphragm 256 forming one Wall of the container 251 to move upwards under the influence of the air forces acting on the diaphragm 256. Thereby the pivot 285 is returned to its original position. The same general thing takes place when the piston valve 296 moves up into the bore 292 to cut off communication between the chambers 266 and 212, thereby placing the chamber 266 at the pressure of the chamber 268. Decrease in pressure of the chamber 266 moves the container 251 upwards, causing the diaphragm 256 to move the rod 255 and the pivot point 285 of the lever 284 on the rod 255 upwards. The pivot point 285 returns downwards to its original position as soon as the restricted openings 258, 259, and 262 in the container 251 can permit the expulsion of suicient fuel from the container 251 to allow the air forces on the diaphragm 256 to return the rod 255 and the pivot point 285 of the lever 284 on the rod 255 to the original position.

To summarize the aforesaid, downward movement of the right end of the control stick 363 may ,be used "to decrease the fuel-air ratio, and up- `in air-flow rate.

18 ward movement of the control stick, to increase the aforesaid ratio. The control stick 363 may be connected with the propeller-pitch governor 21 (Fig. 1) in such a way that if the speed of the propeller I6 is to be increased, the right end of the control stick 363 is moved upwards, increasing the fuel-air ratio. The result is an increase in the temperature of combustion products flowing from the burners I3 to the gas turbine I4 and an increase in the speed of the turbine. Increase in turbine speed produces an increase in speed of the compressor II, and the air-flow rate is proportionally increased, because of the characteristics of the compressor and the gas turbine. The increase in air-flow rate resulting from the increased fuel-air ratio will eventually move the diaphragm 256 upwards sufliciently .to balance the upward movement of the right en'd of the lever 284 due to upward movement of the control stick 363 in the attempt to produce a greater speed, and thereby the piston valve 290 will be returned to its intermediate position of Fig. 4, in which it blocks neither the passage 295 nor the passage 296, and the valve 26| under the influence of the coil spring 216 is returned to its original position, thereby restoring' the original pressure drop across the orifice 263 for a given fuel-flow rate, and accordingly bringing about a return to the original ratio of air-flow rate to fuel-flow rate. The same general thing will take place when the right end of the control stick 363 is moved downwards to raise the piston 296 to restrict the passage 296, thereby reducing the fuel-air ratio. The reduction in pressure in the chamber 266 raises the container 251 causing the diaphragm 256 to raise the rod 255 and the pivot 285 for the lever 284 on the rod. Thus the piston valve 296 is raised farther` into blocking position in the bore 292. After a short time sufficient fuel will have escaped through the openings 258, 259, and 262 in the container 251 to allow the diaphragm 256, the rod 255, and the pivot point 285 for the lever 284 on the rod to return to the original position under the iniiuence of the air forces acting on the diaphragm 256 and the conical spring 249. The lower fuelair ratio reduces the temperature of combustion products going to the turbine |4 and accordingly the speed of the compressor and gas turbine is reduced. The characteristics of the compressor and gas turbine are such that reduction in speed thereof brings about a corresponding reduction This is translated in a reduction in the air pressure difference acting upwards on the diaphragm 256, and the conical spring 249 moves the rod 255 and the pivot pointf285 for the lever 284 thereon downwards suflicient to compensate for the downward movement of the right end of the lever 284 until the left end 0f the lever 284 is returned to its original-,position, bringing the piston 296 to the mid position shown in Fig. 4 between the bores 29| and 292. The removal of the piston valve 296 from the bore 292 re-establishes communication between the unmetered-fuel chamber 212 and the chamber 266 by way of the lines 294 and 296. Thus the pressure in the chamber 266 rises from that of metered fuel to that of unmetered fuel. Accordingly, the valve 26| is lowered to its original position, and the original pressure drop across the opening 263 for a given fuel-flow rate is restored. This means restoration of the original ratio of fuel-iiow rate to air-iiow rate. As the air pressure decreases, for example, with increase in altitude, the aneroid bellows 364 as- '3I`4, the line 3I0, and the element 3H.

s'ociated with the control stick 303 expands, mov- Ying the end of the link connected with the mem- -ber 30| in the arcuate slot 300 nearer the pivot shaft 302 for the control stick 303 and the member 30|. 'Ihus for a given angular movement of the control stick 303, the lower the air pressure, `the lless the movement of the right end of the lever 284. Similarly, the movement of the left 'end of the lever v284 is reduced. Since the impact-pressure-sensing element IIB carries an altitude-correcting capsule |I8a, the pressure difference acting on the diaphragm 250 is dependent upon the weight of air flowing per unit of time, rather than on the volume of Vair flowing. The compressor II and the gas turbine I4 are characterized by an air-flow raterproportional to speed. -as aforesaid, but this air-flow rate is in volume per unit of time rather in .weight per unit of time. Consequently, when a new propeller speed is desired and is selected by adjustment of the propeller pitch governor 2l, the new position of the diaphragm 250 should be responsive to a Volume air-flow rate for the new speed, rather than a weight rate. However, since the diaphragm is responsive to changes in weight airflow rate vbecause of the correcting capsule lita, there lmust be a separate correction applied and .this -is obtained through adjustment of the distance between the connection of the link 299 with the member 30| and its pivot shaft 302.

-A conical spring 24S has been selected to oppose motion of the air diaphragm 25S in the device 245, because the variable rate of the vspring 'provides vcompensation or the fact that vthe air pressure difference acting upwards on the diaphragm 250 in an attempt to compress the spring 249 is proportional to the square of the air flow vrather than to the first power thereof.

The fuel delivered by the apparatus in Fig. 4 through the line 204 may go through a two-pump control such as that shown in Fig. 2 and then go to the burners I3, where it and air coming to the burners by way of a conduit means I9 are transformed to combustion products driving the gas Aturbine I4.

The apparatus of Fig. 5 differs from that of Fig. A4 in that a temperature-responsive device 309 acting to meter the fuel is substituted for the krtemperature-responsive device 4|, which acts to modify air pressure signals transmitted to the air diaphragm. In Fig. 5 the wall |52 of the fuel-metering body is provided with an orifice 3|0, which is controlled by a valve 3| I, comprising 'an enlarged head SI2 'at one side of the wall |62, `a thick stem 3I3 presenting a shoulder .at the other side of the wall |52 and a thin stem 3-|4 connecting the head 3| 2 and the thick stem '3|3. The stem `3I3 is connected to a bellows Sie acting against a fixed stop SI5. A line 3I0 connects the bellows 3I4 and a temperature-responsive element 3H, which is adapted to be positioned in the conduit means I9 so as to be sub- Yjected to temperature of air Iflowing from the regenerator I2 to the burners I3. A liquid expanding with temperature is placed in the bellows A coil spring y3|8 acts between the fuel-metering body and the 4bellows 3M tending to collapse the bellows and serving to insure that in event of escape ofzliquid from the .bellowsf3I4, the line 3IG, or the element 3 I "i, the .bellows will further collapse and the enlarged valve head BIZ will be moved to the left closing the vmetering orice 3I0. In

normal operation-.of the temperature-responsive device 30.0 the Shoulder on the `thick stem 3|.3

will move toward or away from the orifice 23|Il as the temperature ofv air flowing to the burners, sensed by the element 3I'I rises and falls. If the temperature of air sensed .by the element v3|'I increases, the valve stem shoulder moves toward the orifice 3 I0, increasing lthe restriction upon the orifice 3| 0 and the pressure drop across it. Thus there is a greater-*difference in fuel pressure in the chambers |44 and |43 and-an increased upward force acting on the diaphragm I4I. Since the vforce 4acting on air diaphragm |22 remains constant due to a presumably constant air-flow rate, the upward force on fuel diaphagm I4| is greater than the downward force on the air diaphragm |22 and the inner'valve part |49 is raised vto reduce the size of the regulating orice |58. Thereupon the fuel-@flow rate 'is reduced tothe point where the original lower pressure'drop is obtained across the orifice 3I0. This `restoresthe upward force on the `fueldiaphragm to its original value, and the valve part ,I 49 stops itsupward movement. Thus there is obtained a lower ratio of fuel-flow rate to air-ow rate, which lower ratio compensates for the increase in temperature or air'owing to the burners, and the predetermined temperature of combustion products iiowing from the burners to the turbine is maintained.

If the temperature of air flowing tothe burners sensed by the element 3|s'I, is decreased, the Vvalve 3| I moves to the left, causing the restriction of the yorifice 310 to be reduced by movement of the shoulder on the thick stem 3|3 to the left .away from the orifice -3|0.. Thus the pressure .drop across the .orifice 3I0 is decreased, and the .upward force on the fuel diaphragm |4I is decreased. Now the downward force onthe air diaphragm |22 due to a presumably constant airflow rate is greater than vthe upward force on the fuel diaphragm I4I, and the inner valve part |40 is moved downwards, increasing the size of the regulating orice |a. Thereby the fuel-flow rate and the ratio of fuel-,flow rate to air-flow rate are increased. iIf there is failure in the bellows .3|4, line tIS, or temperature-responsive element 3|? resulting in escape of liquid from these parts, the spring SIS moves the bellows 3I4 to the left, causing the Avalve head lI2 to be moved to the left to close opening SII). This increases the pressure difference between -chambers |43 and |44 causing the inner valve part |49 to be moved up to decrease the size of .the regulating orifice I5@a and the fuel-ar ratio. Theresult is a cool safe .running of the turbine I4. YIt doesnotmatter that `the temperature of air flowing tothe burners I3 may increase, forthe .closing of :the orifice 3 I 0. .reduces .the fuel-:air ratio soas to make the turbinesafe for .any temperature of air nowing to the burners.. In the apparatus of Fig. 5, fuel is received from any appropriate source through the conduit |55, which source is not shown, but may be the various parts connected to the conduit |55 in Fig. 2. Fuel isdischarged through the conduit 204 and may go to the kburners by way of a two-pump control such as ond pressures of air in the lair path having a Vdifference indicative of airrfiow rate, said first air pressure exceeding said second air pressure by the amount of said difference and having a communication through which said first air pressure is communicated to the diaphragm, a bellows responsive to density of the air in the air path for variably restricting said communication and being adapted to change the restriction toward its open position under condition of increasing air density, means forming a passage connecting opposite sides of the diaphragm, a bellows responsive to temperature of air in the air path for variably restricting the passage and being adapted to change the restriction from a relatively closed position toward at least one fully open position, and biasing means operative upon failure of the last-named bellows to change the last-named restriction toward at least one fully open position.

2. In a power plant comprising a burner, means forming a path for the flow of air to the burner, means forming a path for the iiow of fuel to the burner, means forming a first orice in the fuel path, means forming a second orifice in the fuel path in series with the first orifice, and means responsive both to the air-flow rate in the air path and to the drop of fuel pressure at the second orifice for controlling the first orifice to regulate the fuel-flow rate in the fuel path, the combination therewith, of means responsive to changes in air-flow rate of short duration for changing the opening of the second orifice to obtain a change in the fuel pressure drop thereat and in the relation of the fuel-flow rate to its effect upon the first-orifice-controlling means for balancing the aforesaid change in air-fiow rate and thereby preventing adjustment of the first orifice to maintain the fuel-flow rate constant.

3. In a power plant comprising a burner, means forming a path for the flow of air to the burner, means forming a path for the flow of fuel to the burner, means forming a regulating orifice in the fuel path, means forming a first metering orifice lin the fuel path in series with the regulating orifice, and means responsive to fuel pressures above and below the metering orifice and to the air-iiow rate in the air path for controlling the regulating orifice to effect a fuel-flow rate in accordance with air-flow rate, the combination therewith, of means forming a second metering orifice in the fuel path in parallel with the first metering orifice and in series with the regulating orifice,V and means responsive to `changes in air-iiow rate of short duration for changing the opening of the second metering orifice to obtain a change in fuel-pressure difference above and below the metering orifices for a given fuel-flow rate for balancing the aforesaid change in air-fiow rate and thereby preventing adjustment of the regulating orifice to maintain the fuel-flow rate constant.

4. In a power plant comprising a burner, means forming a path for the flow of air to the burner, means forming a path for the flow of fuel to the burner, means forming a regulating orifice in the fuel path, and means responsive to fuel-flow and air-flow rates in the fuel and air paths for adjusting the regulating orifice to set the fuelow rate in accordance with the air-flow rate, the combination therewith, of means forming a compensating orifice in the fuel path, and means responsive to changes in air-flow rate of short duration forchanging the opening of the compensating orifice to obtain a change in the relation of the fuel-flow rate to its effect upon 22 the regulating-orifice-controlling means for balancing the aforesaid change in air-fiow rate and thereby preventing adjustment of the regulating orifice to maintain the fuel-flow rate constant, the means for changing the opening of the compensating orifice.

5. In a power plant comprising a burner, means forming a path for the fiow of air to the burner, means forming a path for the fiow of fuel to the burner, means forming a regulating orifice in the fuel path, and means responsive to fuel-fiow and air-fiow rates for adjusting the regulating orifice to obtain a fuel-flow rate in accordance with fuel-fiow rate, the combination therewith, of means forming a compensating orifice in the fuel path, and means for adjusting the compensating orice in response to changes in airfiow rate of short duration to obtain a change in the relation of the fuel-flow rate to its effect upon the regulating-orifice-controlling means for balancing the aforesaid change in air-flow rate and thereby preventing adjustment of the regulating orifice to maintain the fuel-flow rate constant, said last mentioned adjusting means including a container having one wall associated with the compensating orifice, a second wall sensitive to changes in fuel-fiow and air-fiow rates, and a restricted passage for fuel adapted to pass fuel only slowly to and from the container for thereby permitting the container walls to have only slow relative movement.

6. A fuel-metering device comprising means forming an adjustable regulating orifice for fuel, air and fuel diaphragms subjected respectively, to air and fuel pressures indicative of air-now and fuel-flow rates, means connecting the diaphragms with the regulating orifice for regulating the same to maintain a predetermined ratio of fuel-flow rate to air-flow rate, an idle spring associated with the regulating orifice, means forming a passage connecting opposite sides of the air diaphragm, a valve controlling the passage, and means interconnecting the valve and the idle spring for simultaneously causing the valve to open the passage and the idle spring to be shifted away from a position limiting the minimum setting of the regulating orifice and for simultaneously causing the valve to close the passage and permitting the idle spring to return to the position limiting setting of the regulating orifice.

7. In a power plant comprising a burner, means forming a path for the flow of air to the burner, means forming a path for the flow of fuel to the burner, means forming a regulating orifice in the fuel path, means forming a metering orific-e in the fuel path, means responsive to the air-flow rate in the air path and fuel-flow rate in the fuel path for controlling the regulating orifice to regulate `the fuel-flow rate in the fuel path; the combination therewith, of a lever, means associating a first portion of the lever with the metering orifice for adjusting the size of the metering orifice in accordance with the position of the said first portion of the lever, means f-or adjusting a second portion of the lever in accordance with air-flow rate, and means acting against a third portion of the lever to make the leverpivot about the second portion and to move lthe first portion of the lever for adjusting Ithe metering orifice to change the fuel-air ratio, the change in fuel-air ratio producing a speed change of the power plant producing the said second portion of the lever to shift the lever about the third portion as a pivot tol return the first portion .to iits original position, the .metering orifice to .its original. size, ,and the fuel-air ratio to its original value.

.8. .In a power 4plant comprising a gas turbine,

an air compressordriven bythe turbine, a burn-er supplying combustion productsdriving the turbine, means forming a path for the flowV of air from the compressor .to the burner, means forming a path for the `iiow of vfuel to the burner,

rmeans forming a regulating orifice in the fuel path, means forming a .metering orice vin the fuel path, and .means `responsive to air-flow rate in the air path and fuel-flow rate in the vfuel path. for adjusting the regulating orifice to control the fuel-flow rate; the combina-tion therewith, .of yielding means maintaining the site of the .regulating orifice, means .responsive to .change in air-dow rate for adjusting the size of the metering orifice to change the relation of the fuel-flow rate to its effect upon the controlling means for the regulating orice for balancing the aforesaid change in air-how rate and there by Ypreventing; adjustment .of the regulating orifice to maintain the fuel-now rate constant, said last mentioned means including means giving way after a short time to provide for return of the metering orice to its original size under the influence of the `yielding means for making the controlling means for the regulating orice re spend to the change in air-flow rate after the short time, Ya lever, means associating a first portion of ythe lever with the metering orifice for adjusting the size of the metering orifice in accordance with the position of the said first portion of 'the lever, means for adjusting a -second A portion of the lever in accordance with air-:dow rate, and means acting against a third portion of the lever to make the lever pivot about the second portion and to move the first portion of the lever for adjusting the metering orifice to change the fuel-air ratio, the change in fuel-air ratio producing a speed change of the power plant producing the said second portion of the lever to shift the lever about the third portion as a pivot to return the first portion to its original position, the metering orifice to its original size, and the fuel-air ratio to its original Value.

9. In a power plant comprising a gas turbine, an air compresso-r driven by the turbine, a burner supplying combustion products driving the turbine, means forming a path for the ow of air from the compressor to the burner, means forming a path for the ow of fuel to the burner, means forming a regulating orice in the fuel path, means forming a vmetering orifice in the rod and movable with respect to the rest of the container after a short time because of the restricted opening, resilient means for returning the metering orifice to an original size after a short time because of the aforesaid permitted movement of the diaphragm wall with respect to the rest of the container, a lever, means associating a first portion of the lever with the metering orifice for adjusting the size of the metering orifice in accordance with the position of the said first portion of the lever, means connecting .a Ysecond portion of the lever with the rod, and means acting against a third portion of the lever to make the lever pivot about'the seco-nd portion and to move the first portion .of 'the .lever for adjustingthe metering orifice to change the fuelair ratio, the change `in fuel-air ratio producing a speed change of the compressor .and turbine producing a change in air-flow rate acting at lthe said second portion of th-e lever to shift the lever about the third portion as a pivot to return the first portion to its original position, the ,metering orifice to its original size, and the fuel-airratio to its original value.

10. In a power plant, a burner, means forming a path for the flow of fuel to the burner, means forming a path for the iiow of lair .to the burner, means forming a metering orifice in @the .fuel path, means forming a regulating .oriceinthe fuel path, .a fuel diaphragm subjected at. opposite sides to the fuel pressures above and below the metering orifice, an air diaphragm subjected at opposite sides to air pressures in the .air path having a difference indicative of air-flow .ra-te, and means connected with the air and fuel .diaphragme for adjusting the regulating orifice to maintain a predetermined. ratio of fuel-flow rate to air-flow rate; the combination therewith, of means forming passage portions establishing communication between the opposite sides of the air diaphragm, mean-s responsive to temperature of air in the air path for variably restricting a certain. of said passageportions to .make the aforesaid predetermined fuel-air ,ratio vary inversely with the temperature of air in the air path, an idle spring associated with the regulating orifice, a valve controlling another of said passage portions, and means interconnecting the valve and the idle spring for simultaneously causing the valve to open the other passage means and the idle spring to be shifted away from a position limiting the minimum setting of the regulating orifice and for simultaneously causing the valve to close the other passage means and permitting the idle spring to return to the position limiting setting of the regulating orifice.

il. In combination, a burner, means forming a path for the fiow of air to the burner, means forming a path for the flow of fuel to the burner, a fuel valve to control the flow of fuel, a diaphragm connected to the fuel valve and subjected on opposite sides to pressures of air in the air path having a difference indicative of air-flow rate, means comprising passage forming portions establishing communication between opposite sides of the diaphragm, means forming an adjustable restriction in a certain of said passage forming portions and being responsive to temperature of air in the air path for adjustably restricting said certain of said passage forming portions to cause the fuel valve to make the fuelflow rate vary inversely with the temperature of air in the air path, fuel valve positioning means movable from a first position corresponding to a relative low minimum rate of fuel flow caused. by the fuel valve to a second position corresponding to a predeterminedly higher minimum ratev of fuel now caused by the fuel valve, valve means controlling another of said passage forming portions and being shiftable from a first position closing said other of said passage forming portions into a second open position opening said other of said passage forming portions, and mechanical means effective to interconnect said positioning and valve means and being manually movable for substantially simultaneously .shifting both the positioning and the valve means from said first; positions intosaidzsecond positions to insure a fuel flow rate in excess of said relatively low minimum rate and unaffected by fluctuations in air flow.

12. In a power plant, a burner, means forming a path for the fiow of fuel to the burner, means forming a path for the fiow of air to the burner, means forming an adjustable regulating orifice in the fuel path, air and fuel diaphragms subjected respectively to air pressure and fuel pressure differential indicative of air-flow and fuelfiow rates, means connecting the diaphragms with the regulating orifice for regulating the same to maintain a predetermined ratio of fuelflow rate to air-flow rate, an idle spring associated with the regulating orifice, means forming a passage connecting opposite sides of the air diaphragm, a valve controlling the passage and in combination therewith, a manually-set, selected operating condition indicating device including means interconnecting the valve and the idle spring for simultaneously causing the valve to open the passage and the idle spring to be shifted away from a position limiting the minimum setting of the regulating orifice and for simultaneously causing the valve to close the passage and permitting the idle spring to return to the position limiting setting of the regulating orifice.

13. In a power plant, a burner, means forming a path for the flow of fuel to the burner, means forming a path for the flow of air to the burner, means forming an adjustable regulating orifice in the fuel path, air and fuel diaphragms subjected respectively to air pressure and fuel pressure differential indicative of air-flow and fuelfiow rates, means connecting the diaphragms with the regulating orifice for regulating the same to maintain a predetermined ratio of fuelflow rate to air-fiow rate, an idle spring assocoated with the regulating orifice, means forming a passage connecting opposite sides of the air diaphragm, a valve controlling the passage and in combination therewith, a manually-set, selected operating condition indicating device including means interconnecting the valve and the idle spring for simultaneously causing the valve to open the passage and the idle spring to be shifted away from a position limiting the mimirnum setting of the regulating orifice and for simultaneously causing the valve to close the passage and permitting the idle spring to return to the position limiting setting of the regulating orifice, means forming a second passage connecting the opposite sides of the air diaphragm, and means responsive to temperature of air in the air path and operative for variably restricting the second passage to make the aforesaid fuelair ratio vary inversely with the temperature of the air in the air path.

14. In combination, a burner, means forming a path for the fiow of air to the burner, means forming a path for the flow of fuel t the burner, a pressure movable diaphragm, means connected for movement with the diaphragm to control the flow of fuel in said fuel path, said diaphragm being subjected on opposite sides to pressures of air in the air path having a difference indicative of air fiow rate, means forming a passage connecting opposite sides of the diaphragm, a valve-containing valve opening included in said passage, a thermal element responsive to temperature of air in the air path adapted to move said valve in a direction from a position of closely spaced juxtaposition to said valve opening toward a first fully open position as the temperature of air in the air path increases, and biasing means opposing movement, due to said thermal element, of said valve toward said first fully open position and being effective upon failure of said thermal element to move said valve in the opposite direction toward a second fully open position.

15. In combination, a burner, means forming a path for the flow of air to the burner, means forming a path for the flow of fuel to the burner, a pressure movable diaphragm, means connected for movement with said diaphragm to control the flow of fuel in said fuel path, said diaphragm being subjected on opposite sides to first and second pressures of air in the air path having a difference indicative of air flow rate, said first air pressure exceeding said second air pressure by the amount of said difference and having a communication through which said first air pressure is communicated to the diaphragm, a bellows responsive to density of the air in the air path for variably restricting said communication and being adapted to change the restriction toward its open position under condition of increasing air density, means forming a first passage connecting opposite sides of the diaphragm, a bellows responsive to temperature of air in the air path for variably restricting the first passage and being adapted to change the restriction from a relatively closed position toward at least one fully open position, biasing means operative upon failure of the lastnamed bellows to change the last-named restriction toward at least one fully open position, means forming a second passage connecting opposite sides of the diaphragm, and a fixed restriction included in said second passage.

JORMA O. SAR'IO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,279,674 Doble Sept. 24, 1918 2,219,994 Jung Oct. 29, 1940 2,361,227 Mock Oct, 24, 1944 2,367,499 Holley Jan. 16, 1945 2,384,282 Chandler Sept. 4, 1945 2,392,055 Mennesson Jan. l, 1946 2,405,888 Holley Aug. 13, 1946 2,407,115 Udale Sept. 3, 1946 2,447,261 Mock Aug, 17, 1948 2,447,267 Mock Aug. 17, 1948 2,465,550 Orr Mar. 29, 1949 2,486,223 Stresen-Reuter Oct. 25, 1949 2,529,100 Orr Nov. 7, 1950 2,545,703 Orr Mar. 20, 1951 

